The present invention relates to an adjustable support and in particular, but not exclusively, to an adjustable support arm for a computer terminal.
A computer terminal placed on a desk top may not be ideally positioned to suit the needs of every operator. An operator may find that the terminal is too high, too low, or too far from the edge of the desk for convenient operation, and may find that the terminal is tilted at an angle which makes it hard for the operator to easily view the terminal's screen. Thus it would be advantageous if an operator could easily adjust the elevation, horizontal position and tilt of the terminal. Also, since a computer terminal placed on a desk top takes up valuable workspace, it would be advantageous if a terminal positioned above a desk could be easily moved aside when not in use.
Various support apparatus have been developed to provide for flexible repositioning of a computer terminal U.S. Pat. No. 4,589,621 entitled "Ergonomic Monitor Stand", issued to Hunt et al, May 20, 1986, describes a computer monitor stand comprising a platform for holding the monitor and a vertically extendable linkage for supporting the platform above a rotatable base. The Hunt et al stand allows the vertical position of the monitor to be adjusted, allows the monitor to be rotated about a vertical axis, and allows the monitor to be tilted about a horizontal axis. However, the stand does not permit the monitor to be moved horizontally.
U.S. Pat. No. 4,562,987, entitled "Computer Terminal Support with Five Degrees of Freedom", issued to Leeds et al, Jan. 7, 1986, discloses a terminal support for flexibly positioning a computer terminal above or to the side of a desk. The support, which allows the computer terminal to be moved in horizontal and vertical directions and to be rotated about vertical and horizontal axes, includes a platform for holding the computer terminal and a pair of horizontally disposed, pivotally linked, swivel arms for flexibly positioning the platform within a horizontal plane. A first collar attached to one end of one of the swivel arms slips over a king post clamped to the edge of a desk. A support collar mounted on the king post below the first collar includes a set bolt for fixing the vertical position of the first collar on the king post. To raise or lower the computer terminal, an operator must loosen the set bolt, raise or lower the support collar, support assembly and terminal, and then tighten the bolt. Inasmuch as the set bolt may be attached to the rear of the desk, it may be difficult for an operator to access it. In addition, while adjusting the vertical position of the monitor, the operator must support the full weight of the monitor and support assembly, which may be quite heavy. If the operator accidentally drops the assembly during the adjustment process, or if the operator does not adequately tighten the bolt, the support assembly will slip on the king post and strike objects on the desk below, and the resulting impact may damage the terminal.
U.S. Pat. No. 4,591,122 entitled "Support Structure with a Support Arm Pivotal for Height Adjustment", issued May 21, 1986, to Kreuzer, discloses a support structure having an arm comprising two parallelogram structures integral therewith. A compression spring forms one side of one of the parallelogram structures and is used to counter balance the weight of an apparatus being supported. A rod of variable length forms a portion of the other parallelogram structure. To fix the arm in a particular position, the rod length is adjusted so as to add to or relieve spring compression to stabilize the arm in a new position. Additional compression springs are required for the support of heavier apparatus. The use of compression springs and variable length rods to form the arm makes the support complex and costly.